A feasibility study of polymers which respond to variations in glucose concentration and could be used in an insulin delivery device will be performed. Expansion of the polymers in response to elevated glucose levels would allow insulin to escape from a reservoir into the body. When the insulin has reduced the glucose concentration, the polymer would contract, thereby slowing the delivery of insulin. This type of device would be much simpler than electromechanical insulin delivery systems and would be automatically responsive to glucose. The membranes are made from hydrogels and may therefore prove to be biocompatible. A project involving professionals in the disciplines of biochemistry, polymer chemistry, chemical engineering, and medicine is proposed to perform the following research: 1) The properties of immobilized glucose oxidase enabling it to serve as a suitable catalyst for gluconic acid formation will be studied over wide ranges of pH, glucose and oxygen concentration, enzyme loading, glucose transients, and times and conditions of storage of immobilized glucose oxidase. 2) Acrylic copolymers will be synthesized, characterized, and optimized to achieve appropriate responsiveness to gluconic acid and allow high enzyme activity and stability. Water content, swelling kinetics, molecular weight between crosslinks, permeability, suitability for enzyme immobilization, internal pH induced by glucose and sensitivity of the enzyme/polymer system to glucose will be investigated. 3) Transport of insulin and other molecules through the polymers as a function of pH and glucose concentration will be measured and used to further develop and optimize the design of the device. 4) The feasibility of the membrane for controlling insulin delivery in a biological milieu will be investigated. Membrane fouling by biological fluids, tissue reactions to the polymer and rates of insulin delivery achievable by prototype devices will be studied. Since swelling of the membrane in response to glucose is easily measured, the membranes could also be used as glucose sensors and help provide glucose control when used with pumped insulin delivery systems.